Improved the VirtualOutlet boundary condition to handle interaction with BounceBack and NoDynamics nodes.

Added masked versions for the sponge zones.

Added and improved STL utilities.

Changed the STL file reader to handle more general files.

Added a new bubble-pressure model in the updateBubblePresure function.

Major revision of the mrt implementation (w and w/o force, w and w/wo smagorinsky model or a combination of both, including quasic incompressible models). The code has been tested for mrt and forced mrt. The smagorinsky model still needs to be tested and validated.